ComputationalStudiesofthethermodynamicsofthehydrationof organic compounds have been mostly limited to the computation of the free energy of hydration ?Ghydr. The enthalpic and entropic components have not been thoroughly investigated because of the computational cost required to obtain converged results for these two quantities. Due to this problem, older studies exhibited huge statistical errors. We have recently observed that calculated entropies and enthalpies of hydration of several organic compounds often showed opposite trends with respect to the experiments. On the other hand, the corresponding free energies of hydration were, in most cases, in agreement with the experiments as the discrepancies in the entropic and enthalpic components canceled each other when combined. A systematic study of this phenomena is underway. A. Scientific Subproject